Safety stop for traveling structures



Oct. 6,1925. 5 7 1,555,831

A. F.- CASE SAFETY STOP FOR TRAVELING STRUCTURES Filed April 1'7 1922 3Sheets-Sheet l A. F. CASE SAFETY STOP FOR TRAVELING smuc'sunss ssheets-sheet 2 Fild April 1'7, 1922 Oct 6, 1925.. I ggg g g A. F. CASE;Y

SAFETY STOP FOR TRAVE'LTNG STRUCTURES Filed Aprii' 1m 922 3SheetS--Sheet s a n Ma 7% ab Patented Oct. 6, 19 5 UNITED STATES PATENTOFFICE.

ARTHUR F. CASE, OF CLEVELAND, OHIO, ASSIGNOR TO THE WELLMAN-SEAVEBJEOR;GAN COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

SAFETY STOP FO'R TRAVELING STRUCTURES.

Application filed April 17, 1922. Serial No. 554,080.

To all whom it may concern:

Be it known that I, A THUR F. CASE, a citizen of the United States,residing at Cleveland, in the county of Cuyahoga and State of Ohio, haveinvented a certain new and useful Improvement in Safety Stops forTraveling Structures, of which the following is a full, clear, and exactdescription.

This invention relates to what may be termed a safety stop forstructures adapted to travel along a trackway, and has particularreference to a safety stop for material conveying bridges, to hold thestructure against movement by wind pressure on it.

Large traveling bridges have on more than one occasion been wrecked bybeing impelled along the trackway by wind pressure notwithstanding theapplication of friction brakes, and to avoid wreckage of travelingstructures such as these bridges, track clamps have been provided, twoor more of which have been secured to each supporting leg of the bridge,these clamps consisting of pairs of jaws which are designed to be set bycounterweights to frictionally engage opposite sides of the rails, andto be released by power usually derived from one or more electric motorswhich lift the counterweights and thus disengage the jaws from the trackrails when the structure is to be moved along the track.

The car clamps heretofore employed have not proven to be entirelysatisfactory, for bridges are known to have been wrecked notwithstandingthe factthat they were equipped with a series of the rail engagingclamps which though set to engage the rails as tightly as the nature ofthe apparatus permitted, were not effective to hold the structureagainst drifting along the trackway under the pressure of an unusuallyheavy wind. Furthermore, aside from the fact that the prior clamps donot afford absolute protection, they are as a rule very complicated byreason of the fact that they involve great deal of apparatus in the wayof cables, sheaves and hoists scattered throughout the structure andextending from the lower portions of the supporting legs up to and alongthe bridge proper to the point where the clamps are designed to becontrolled. Because of all this apparatus used in conjunction with thecar clamps themselves, and required for their operation,

the clamps often get out of order and for that reason are unreliable.

The principal objects of the present inventionare to provide first anefficient stop which is not solely dependent upon the frictionalgripping of clamp members to the sides 'of the rails to hold thestructure against movement, but has a more reliable and a more efiicientholding device in the form of a wedge which is designed to be insertedbetween the wheel and the track.

Further the invention aims to provide a safety stop in the form of aself contained unit having to a marked degreethe advantage ofsimplicity, and which is free of all complicated operating parts sosusceptible to injury and derangement, such as ropes, sheaves, windingdrums and the like.

Still further the invention aims to provide a safety stop in the form ofa unit located next the runway where the location is favorable forexamination and where repairs can be easily made.

Finally it is the aim of the invention to provide a safety stop, aseries of which can be readily applied to old as well as new travelingbridges.

The safety stop involving my invention, is as far as I am aware, new instructure and principle, particularly so far as safety stops areconcerned adaptable in a commercial or practical way especially forstructures of the type for which my device is designed to giveprotection.

This stop has a number of new features which are not necessarilycombined in one structure, but are susceptible ofadvantageous conjointuse to provide maximum efficiency. Among these features is a wedgeadapted to be lowered onto the track and under the wheel to positivelyblock its movement; a device which may be in the form of a clamp forengagement with the rail to prevent the wedge being pushed along thetrack by the wheel of the structure; also power operated means foractuating the wedge and clamp; an arrangement wherein all these partsare in a self contained unit, preferably suspended from the leg of thebridge; also an arrangement wherein the parts are set by a counterweightand released by a motor, with the motor itself arranged to serve as acounterweight.

The above and other features constitute my invention which may bebriefly summarized as consisting in certain novel details ofconstruction, and combinations and arrangements of parts which will bede scribed in the specification and set forth in the appended claims.

In the accompanying sheets of drawings wherein I have illustrated anembodiment of the invention which operates with high efficiency, Fig. 1shows a side elevation of a material conveying traveling bridge forwhich my invention is particularly utilized, it being intended that twoor more of my improved safety stop devices be provided on each leg orsupporting part of the bridge; Fig. 2 is an end view of the lowerportion of one of the legs of the bridge showing the lower stillprovided at its ends with my improved safety stops, each adapted to stopthe movement of the structure in one direction along the trackway; Fig.3 is an enlarg;d side elevation of the safety stop showing the sameattached to the sill, a portion of the latter and a portion of the trackwheel with which the wedge co-operates being shown; Fig. 4 is an endview of the same, with the rail in section; Fig. 5 is a view similar toFig. 3, showing the safety stop applied or set so as to hold thestructure against movement, whereas in Fig. 3 it is shown released.

Referring now to the drawings, in Figs. 1 and 2 I have shownconventionally a material conveying traveling bridge in connection withwhich my invention has particular utility. The bridge comprises an upperhorizontal portion or bridge proper 10, supported on legs 11 providedwith trucks having wheels 12 adapted to travel along the bridgetrackway. In some instances the truck wheels on each side travel over asingle rail as herein illustrated and in other instances along doublrails, but whether there are two rails or a single rail on each side ofthe trackway is immaterial to the present invention.

In accordance with the present invention as herein illustrated, I attachto the lower sill 18 of each leg 11 a pair of my safety stop devices,preferably provided forward of the front wheel of the forward truck andbehind the rear whtel of the reartruck so that movement of the bridge ineither direction may be prevented.

By reference to Figs. 3, I and 5 it will be seen that each safety stopis in the form of a self contained unit which is suspended from thesill, it being a feature of the present invention that a rigidconnection between the stop and sill of the bridge leg is unnecessary.

The stop comprises a casting or body member 14;, adapted to be swung toand from engagement with the rail as shown. The lower part of thecasting is provided with feet or flange-like members 15 which at alltimes extend down freely along opposite sides of the rail to keep thecasting central over the rail, and the casting is pro vided also with awedge or nose 16 having a part curved in conformity with the curvatureof the truck wheel 12 so that it can be insert id between thewheel andrail to produce the effect of a blocking wedge when the casting islowered onto the rail.

It is desirable that means be provided to keep the wedge from slidingalong the rail, and while this may assume different forms, it consistspreferably of a pair of clamp levers 17 pivotally supported at 18 onopposite sides of the casting 1d so as to be capable of swinging in aplane transverse to the casting and to the rail. These clamp leverswhich are pivoted between their ends, are provided at their lower endswith rail engaging jaws 18*, and at their upper ends they are connectedin this instance by links 19 to crank arms 20 pivotally or rotatablysupported by means of pins or short shafts 21 journaled in bosses 22 onopposite sides of and at the upper front part of the casting 14. Thesepins carry bevel gears segments 23 which mesh with a double bevel gearsegment 24 which moves up and down between the bevel gear segments 23,and this double bevel gear segment is carried by an operating arm 25pivotally supported by means of a pin or stud 26 mounted in bosses 27 atthe top central portion of the casting 14:. The opposite end of this arm25 is extended to form a support 28 for a motor 29 forming a part of thself contained unit referred to, and serving both as a counterweight toset the stop in operative position, and also as a power means by whichthe stop is operated.

In this instance the motor drives a worm 30, indicated by dotted linesin Figs. 3 and 5, and this worm engages a worm wheel 31, both the wormand the worm wheel being carried by the arm and enclosed in a portionthereof forming a gear case 32*. The worm wheel 81 is on a shaft 82extended to each side of the arm 25 to form a support for two liftinglevers 33 provided at their free ends with rollers 34 adapted to roll onthe inclined top surface of the rear portion 35 of the casting 14;.

The parts are so arranged that the rotation of the motor in onedirection causes the lifting levers to exert a pressure on the maincasting and lift the motor end of the pivoted arm 25. This causes thebevel pinions 23 to revolve in the proper direction to release the gripof the clamps on the rail, and also has the additional effect of liftingthe unit away from the wheel and rail to inoperative position, as willbe explained, the parts then being in the position shown in Fig. 3. Itmight be stated that when the parts reach the position shown in thisfigure, the rollers the motor is stopped, preferably automatias alreadystated.

cally, but the motor. controlling switch may be in the form of a limitswitch onthe arm 25. Such a device being common in the art forms no partofthe present in vention and is not illustrated herein.

hen the'motor'revolves in the opposite direction'the lifting levers 33are reversed and the motor end of the pivot-ed arm descends by gravity,this motion causing the clamps to grip the rail. As soon as this grip iseffected, the pivoted arm 25 with the motor 29 serving as acounterweight ceases to rotate onits axis 26, and continued rotation ofthe'lifting arms causes the rollers to leave their path on the maincasting 14, thus allowing the full weight of the motor and itsassociated parts to act as a counter- Wveight to maintain the grip ofthe clamps 17 on the rail. However, prior to the time that the clampsengage the rail the unitswings down onto the rail or to the positionshown inFig. 5, so that the wedge16 is inserted between the wheel '12and rail. When the levers 33 reach substantially the position showninFig. 5,"the motor is stopped preferably automatically by a limitswitch not shown.

The safety stop when in operatingpo'sition rests on the runway rail andhas no rigid connection whatever with the bridge For the purpose ofsuspending the stop when in inoperative position, or while the bridgeis'in'motion, forward and rear suspending links 37 and 38 are provided;In this instance there is a single forward link '37, and preferablythere are a pair of the rear links 38 extending entirely upwardly towardthe sill on 0pposite sides of the casting and pivoted arm 25. Theforward link is pin connected at 39 to the upper front part of thecasting 14,

and the rear links arepin connected at 40 to the rear part of thecasting 14. The upper ends of the links have slotted holes for pins 41by which the links are connected to brackets 42 on the under side of thesill 13 of the bridge leg. The upper pins 41 are forward or toward thewheel from the pins 39 and 40 by which the lower ends of the links areconnected to the casting, so that the effect of gravity will be to swingthe casting downward and inward onto-the rail and between the wheel andrail.

It is apparent from this arrangement that if a force is applied tocausethe casting to move in a direction away from the wheel,

the links will cause it to move forwardly as well as outwardly, with theresult that the wedge end 16 of the casting is withdrawn from contactwith the wheel, and at the same time thecasting 14 is liftedoif-therail. In'this position thestop is out of ser vice, and issupported from the sill by the suspending links; For the purposeof'exerting the necessary force to cause this move ment of the stop, alifting link 43 is provided. This link is in this instance connectedtothe pin 41 by which the rear links 38 are connected to the sill, andthe lower end of this link is provided with a slotted hole 44, receivinga pin 45 carried by the upper inner end of the pivoted arm 25, thelocation of these pins being such that the top pin of the lifting linkis back of, and above or further away from the wheel thanthe pin 45 onthe pivoted arm.

Due to the position of thislifting link 43, it forms an approximatediagonal of the equilateral connecting the four pins of the supportinglinks 37 and 38. Itis evident that a force which causes this diagonal toshorten will cause the other diagonal to lengthen, and inasmuch as anychange in this length must-necessarily change'th'e position of the linkpins 39'and 40', relative to the corresponding pins-on the-bridgesil-l13,

the lengthening of'this. diagonal distance,

i. e. the long diagonal, will cause the-entire stop unit to swing awayfrom the wheel and rai The lifting link 43 is of such lengththatwhen thepivoted arm is being swung upward and has released the clamps, the pin45 of the arm engages the end of the slotted l1o'le'44 of the liftinglink 43, and a further rotation of the arm exerts a pull on thislinkwhi'ch produces the effect of shortening the diagonal which thislink approximates as above stated, and the stop is thereby lifted to theout of service position shown in Fig. 3.

On the other hand, when the motor 29 is operated to lower the motor endof the pivoted ar1n25, the initial rotation or downward swingingmovement of the arm relieves the lifting force and the unit graduallyswings by gravity to operative position onto the rail with the wedgeunder the wheel as shown in Fig. 5, and further downward swingingmovement of the arm 25 applies theclamp arms 17 as already explained.

As previously stated, the upper ends of the suspending links areprovided with slotted holes, the purpose being to allow for slightmovement of the bridge toward the safety stop after the clamps havebeenset without producing compressive stresses in the links.

As before stated, each traveling bridge has a series of the safety stopsabove described; that is to say, two or more on each leg of the bridge.The several motors of the stop devices are preferably controlledsimultaneously through i3l16"1116ll11111 0f a single controller or froma single controlling pointpreferably located at the operators station onthe bridge proper, and the controlling wires will be extended along thebridge and down the legs and will be connected to the motors in anysuitable manner, such control devices being common in the art they arenot herein illustrated.

When the bridge is stationary all the safety stop devices will be set asshown in Fig. 5, the motors 29 then being de-energized, and when thestop devices are in the position shown in Fig. 5 the wedges are setbetween the track rails and the truck wheels and the clamps are held bythe counter weighted levers in clamping engagementwith the sides of therails so as to prevent the wedges moving along the rails.

When it is desired to move the bridge along the trackway, the motors 29of the several stop devices are energized and operated in a directionsuch that the lifting levers 38 are rotated so as to cause the rollers54k to be lowered onto the rear inclined surfaces of the castings 1i,and then to travel in" wardly along the same so as to lift the pivotedlevers 25 from the position shown in Fig. 5 to the position shown inFig. 3. This movement of the pivoted arms 25 first causes the clamps tobe released from the rails and then causes the units to be bodily swungto the inoperative position shown in Fig. 3, and when the lifting leversreach the depressions in the castings, the motors are automaticallystopped and the pivoted levers 25 with their motors are retained inlifted position with the clamps released and the wedges withdrawn fromthe rails and wheels.

lVhen the bridge has been moved to the point desired, the safety stopsare again set, this being done by simultaneously operating the motors inthe-opposite direction so as to rotate the lifting arms 33 in thereverse direction and lower the pivoted arms 25. As the arms 25 swingdownward the body members or castings 14 of the several stop de vicesswing down onto the rails with the wedges between the rails and thetruck wheels and then set the clamp, and after the lifting arms orlevers 33 and their rollers 34 move clear of the castings so that thewhole weight of the arms 25 with their motors act to hold the clamp jawsin engagement with the rails the motors will. automatically stop.

Thus it will be seen that I provide safety stops which embody many newfeatures, and that the objects stated at the beginning of thespecification are attained to a very high degree. Though I have shownonly the preferred construction, various changes may be made, and I donot desire to be confined to the exact details shown, but aim in myclaims to cover all modifications which do not involve a departure fromthe spirit and scope of my invention.

Having described my invention, I claim:

1. A safety stop for traveling structures movable along a trackwaycomprising a wedge adapted to be inserted between a wheel of thestructure and a rail, movable means associated with the wedge andengageable with a portion of the trackway for preventing the wedgesliding along the rail, and means for actuating the first mentionedmeans and for shifting the wedge.

2. A safety stop for traveling structures movable along a trackway,comprising a wheel blocking wedge engageable between the rail and wheeland a rail engaging clamp.

3. A safety stop for traveling structures comprising a wheel blockingwedge engageable between the rail and wheel a rail e11- gaging clamp,and means for withdrawing the wedge and releasing the clamp.

l. A safety stop for traveling structures movable along a trackway,comprising a eounterweighted clamp and a wheel blocking wedge engageablbetween the rail and wheel.

5. A safety stop for traveling structures movable along a trackway,comprising a rail clamp and a gravity actuated wheel blocking wedgeengageable between the rail and I wheel.

6. A safety stop for traveling structures movable along a trackway,comprising a wheel blocking wedge adapted to be inserted between a wheeland a rail and a rail clamp for preventing movement of the wedge alongthe rail, and power means for releasing the clamp and lifting the wedgeout of operative position.

7 A safety stop for traveling structures movable along a trackway,comprising a wheel blocking wedge adapted to be inserted between a wheeland rail, a rail engaging clamp for preventing movement of the wedge, acounterweight for setting the clamp, and power means for swinging thewedge from operative position and for releasing the clamp.

8. A safety stop for traveling structures movable along a trackway,comprising a movable member adapted to be lowered onto a rail of thetrackway, and provided with a wheel blocking wedge adapted to beinserted between a wheel and a rail, rail gripping means carried by thewedge and engageable with a portion of the trackway to prevent movementof the wedge along the rail, and means operable to move said firstmentioned means out of engaging position and to shift said member awayfrom the wheel.

9. A safety stop for traveling structures movable along a trackway,comprising a member supported from the structure and having a wedge forinsertion between a wheel of the structure and the rail and having alsoa rail engaging clamp.

Inn

10. A safety stop for traveling structures comprising a unit including awedge movable into and out of a position between a wheel of a structureand the rail,-a rail engaging clamp, and an operating motor foractuating the wedge.

11. A safety stop for traveling structures movable along a trackwaycomprising a movable member having a wheelblocking Wedge, and a motormounted on said movable member for actuating said-member.

12. A safety stop for traveling bridges comprising a bridge proper witha supporting leg, and a safety stop device in the form of a unit movablysuspended from the leg and including a wheel blocking wedge and a railclamp.

13. A safety stop for traveling bridges, comprising a bridge properwith'a supporting leg, and a safety stop in the form of a unit movablysuspended from the leg and including a wheel blocking wedge,- a railclamp, and an operating motor for actuating the Wedge and clamp.

14. A safety stop for traveling structures movable along a rail,comprising a member having a rail blocking Wedge, andamotormounted onsaid member and serving to shift said member. I

15. A safety stop for traveling structures movable along a trackway, atrack engaging member mounted for movement by gravity into trackengaging position, releasable means for holding said member in raisedposition, a rail engaging clamp carried by said member, and means forreleasing said member and operating said clamp.

1-6. A safety stop for traveling structures movable along a trackway, atrack engaging member mounted for movement by gravity to track engagingposition, a rail clamp carried by said member, means for actuating saidclamp, and releasable means for holding said member in raised positionand said clamp in open position.

17. A safety stop for traveling structures movable along a trackway, awheel blocking wedge mounted for movement by gravity into operativeposition between the wheel and rail, a rail engaging clamp carried bysaid wedge, a counterweight for operating said-clamp, and releasablemeans for holdingsaid wedge and said clamp counterweight inraisedposition.

18. A safety stop for traveling structures movable along a trackway, atrack en ag ing member mounted for movement by gravity into trackengaging position,-a rail clamp carried by said member, a lever foractuating said. clamp, means for holding said member in raised positionand said clamp in openposition, and means for releasing said member andoperating said lever to set said clamp'.

19; A safety stop for traveling structures movable along a tracldway, amovably' mounted wheelblocking wedge, and means for successively movingsaid wedge into engagement between the wheel and rail, and

clamping said wedge to the rail. v

20. A. safety stop comprising a member inounted to move by gravity intorail engaging as a counterweight to move said memher in one directionand operable to move said member in the opposite direction.

22. A safety stop for traveling structures, comprising'a trackengagingstop member, a combined motor and counterweight movably mounted on. saidstop member, and means actuated by said motor operable. on move-' mentof the motor in one direction to move said stop member in one directionand on movement of the motor in the opposite directio'nto release saidmotor and permit it to act asacounterweight tomove said stop member inthe opposite direction.

'23. A safety stop fortraveling structures, comprising a unit includingatrack engagingstop member, suspension members connected thereto andadapted to be secured to said traveling structure, and a lever pivotedon said stop member andadapted to coact with said suspension members toraise or lower said stop member.

24. A safety stop for traveling structures comprising a unit including atrack engaging stop member, suspension members connected thereto andadapted to be secured to said traveling structure, a lever pivoted onsaid stop member and, adapted to 'coact with said suspension members toraise or lower saidistop member, and a motor mounted on said unit andadapted to actuate sai'd 'lever to raise or lower said stop member.

25. A safety stop'for traveling structures movable along a trackway,comprising a track engaging member adapted to be movably suspended fromsaid structure, and means carried by said movable member adapted toactuate the same to movesaid member into and out of engagement with apart" of said trackway. g

26; A safety stop for traveling structure's movable along a t'mckwaycomprising a track engaging member adapted to be movably suspended fromsaid structure, and a motor carried said movable member, adapted toactuate thesame to move' said member into and out ofengagement with apart orysaidaackway. g H

27. A safety stop: for traveling structures movable along a trackway,comprising a wedge member adapted to be suspended from said structurefor movement into engaging position between a wheel of said structureand the rail and to a position out of engagement with said wheel andrail, and actuating means carried by said wedge member adapted to movethe same into or out of position between a wheel of said structure andthe ra1l and to a position out of engagement wlth said wheel and rall, aclamp carried by said wedge member and engageable with the rail, andmeans carried by said wedge member adapted to move the same into or outof engaging position and to move said clamp into or out of engagementwith the rail.

29. A safety stop for traveling structures movable along a trackway,comprising a track engaging. member, a pair of links pivoted to saidmember and adapted to be suspendedfrom spaced pivots on said structurewhereby said member maybe raised or lowered by swinging movements ofsaid links, and means carried by said track engaging member whereby saidmember may be moved into or out of engagement with a part of saidtrackway.

30. A safety stop for travelingstructures movable along a trackway,comprising a body member, a rail clamp carried by said body member, anactuating lever for said clamp carried by said body member, said leveron movement in one direction being adapted to actuate said clamp to gripthe rail and on movement in the opposite direction to release saidclamp, and actuating means mounted on said lever for swinging it ineither direction.

31. A safety stop for traveling structures movable along a trackway,comprising a body member, a rail clamp carried .by said body member, anactuating member for said clamp carried by said body member, said memberon movement in one direction being adapted to actuate saidclamp to gripthe rail and on movement in the opposite direction to release saidclamp, a motor mounted upon said member and forming a counterweight tomove said member in one direction, and means actuated by said motor tomove the member in the opposite direction.

32. A safety stopfor traveling structures movable along a trackway,comprising a body member adapted to be supported from said structure andhaving a rail engaging part and an actuating lever mounted on said bodymember, said lever having a counterweight thereon adapted to shift thesame in one direction and said lever having means thereon engageablewith said body member to shift said lever in opposition to saidcounterweight.

33. A safety stop for traveling structures to actuate said lever in onedirection, and a crank arm on the motor shaft engageable with said bodymember for shifting said lever in opposition to said counterweight.

34. The combination with a traveling structure adapted to be moved alongatrackway, of a track engaging unit comprising a body member, links formovably suspending said member from said structure, a counterweightedlever carried by said body member, said lever being connected with oneof said links whereby on movement thereof in one direction said unit israised and on movement in the opposite direction said unit is loweredinto track engaging position.

35. The combination with a traveling structure adapted to be moved alonga trackway, of a track engaging unit comprising a body member, links formovably suspending said member from said structure, a lever carried bysaid body member, said lever being connected to one of said linkswhereby on movement thereof in one direction said body member is loweredinto track engaging position and on movement thereof in the op positedirection said body member is raised to inoperative position, andactuating means for said lever carried by said unit.

36. The combination with a traveling structure adapted to be moved alonga track Way, of a self contained unit comprising a track engaging bodymember, suspension members for movably connecting said body member tosaid structure, and means carried by said body member and co-operatingwith said suspension members to raise and lower said body member intoand out of track engaging position.

37. The combination with a traveling structure adapted to be moved alonga trackway, of a self contained unit comprising a track engaging bodymember, spaced suspension links connecting said'structure and bodymember, whereby said body member is raised and lowered upon swingingmovement of said links, a motor carried by said unit, and means alsocarried by said unit and actuated by said motor to move said linksangularly with respect to said body member so as to move the latter.

38. The combination with a traveling structure adapted to be moved alonga trackway, of a self contained unit comprising a track engaging body1nember,front and rear links connecting said body member to saidstructure, a diagonally disposed device for moving said links angularly'with'respect to said body member to shift the same, and means carried bysaid unit for actuating said device.

39. The combination with a traveling structure adapted to be moved alonga trackway, of a self contained unit comprising a track engaging'body'member having a wedge portion engageable between a wheel of saidstructure and the rail upon which it runs, links connected at one end tothe body member and at the other end to the structure for suspendingsaid body member from said structure, said links being disposed at anangle to the vertical whereby said body member tends to move by gravitydownwardly and longitudinally with respect to the rail to bring saidwedge portion thereof into engagement between the wheel and rail, a railclamp carried by said unit, and a single actuating means for swingingsaid links to shift the body member and for operating said clamp.

40. The combination with a traveling structure adapted to be moved alonga trackway, of a track engaging unit comprising a body member, linksconnecting said member with said structure, said links being pivoted atone end to the body member and at the other end to the structure, andmeans carried by said body member and connected with one of said linkswhereby on movement thereof in one direction said body member is raised,

and on movement thereof in the opposite direct-ion said body member islowered.

41. The combination with a traveling structure adapted to be moved alonga trackway, a track engaging unit comprising a body member, linksconnecting said member with said structure means carried by said bodymember and connected with one of said links whereby on movement thereofin one direction said body member is raised, and on movement thereof inthe opposite direction said body member is lowered, and a rail engagingclamp carried by said body member, said clamp being adapted to beoperated by said means whereby when said body member is lowered saidclamp is actu- ,ited to grip the rail.

4-2. The combination with a traveling structure adapted to be movedalong a trackway, of a track engaging unit comprising a body member,links connecting said member with said structure, and a counterweightedlever carried by said body member, said lever being connected with oneof said links whereby on movement thereof in one direction said bodymember is raised, and on movement thereof in the opposite direction saidbody member is lowered.

43. The combination with a traveling structure adapted to be moved alonga trackway, of a track engaging unit comprising a body member, linksconnecting said memwith said structure, a counterweighted lever carriedby said body member, said lever being connected with one of said linkswhereby on movement thereof in one direction said body member is raised,and on movement-thereof in the opposite direction said body member islowered, a rail engagin'g clamp carried by said body member and adaptedto be operated'by said lever, and means carried by said unit foractuating said lever in opposition to said counterweight.

44. The combination with a traveling structure adapted to be moved alonga trackway, of a track engaging unit comprising a body member, linksconnecting said member with said structure, a lever carried by said bodymember, a motor mounted on said lever and forming a counterweighttherefor adapted to shift said lever in one direction by gravity, saidlever being connected with one of said links whereby on movement thereofin one direction said body member is raised and on movement thereof inthe opposite direction said body member is lowered.

45. The combination with a traveling structure adapted to be moved alonga trackway, of a track engaging unit comprising a body member, linksconnecting said mem ber with said structure, a lever carried by saidbody member, a motormounted on said lever-and forming a counterweighttherefor adapted to shift said lever in one direction by gravity, saidlever being connected with one of said links whereby on movement thereofin one direction said body member is raised, and on movement thereof inthe opposite direction said body member is lowered, a rail engagingclamp carried by said body member and adapted to be operated by saidlever, and means actuated by said motor for shifting said lever in thedirection opposite to the gravity movement thereof.

as. The combination with a traveling bridge having supporting legstraveling along spaced rails, each of said legs having front and rearwheels, of stop devices supported by said structure in front of saidfront wheels, and at the rear of said rear wheels, each of said deviceshaving a member provided with a rail clamp and a wedge portionengageable between the adjacent wheel and rail, the wedge portion ofeach of said devices being mounted for movement downwardly and towardthe adjacent wheel into blocking position.

47. he combination with a traveling bridge having supporting legstraveling along spaced rails, each of said legs having front and rearwheels, of stop units supported from said structure in front of saidfront wheels and at the rear of said rear Wheels, each of said unitshaving a body member provided with a Wedge portion engageable betweenthe adjacent Wheel and 10 front and rear Wheels, of stop devicessupported by said structure in front of said front wheels, and at therear of said rear Wheels, each of said devices having a member providedwith a Wedge portion engageabie between the adjacent Wheel and rail, anda rail engaging clamp.

In testimony whereof, I hereunto affiX my signature.

ARTHUR F. CASE.

